Abstract The University of Wisconsin Comprehensive Cancer Center (UWCCC) Flow Cytometry Laboratory (Flow Lab) is a heavily utilized shared service on the University of Wisconsin-Madison campus available to researchers who are members as well as non-members of the UWCCC. The impact of the Flow Lab on biomedical research infrastructure at UW-Madison is significant. This High-End Instrumentation Grant is a request for funds that cover 77.5% (remaining 22.50% supported by the institution) of the total cost of a BD FACS Symphony? instrument to further expand single cell analysis capabilities into the 30+ parameter range. Single cell analysis by flow cytometry is in the midst of an explosion of technologies and reagents to support such high parameter analyses. Current users are pushing the limits of existing technologies with panels in the 12-18 color range. The experienced staff, well-established daily Quality Control Procedures, Online Scheduling System, Educational Programs and the Computational and Statistical support available at the University of Wisconsin allow for seamless integration of the BD FACSymphony into the Flow Lab. The BD FACSymphony will impact the development of novel treatment strategies for various human pathologies and increase our understanding of human biology. The BD FACSymphony will support the research of seven major users- (i) clinical trials for development of a prostate cancer vaccine (PI, McNeel), (ii) development of anti-fungal and antimicrobial immunity (PI, Klein), (iii) understanding molecular mechanisms in leukemia and hematopoiesis (PI, Zhang), (iv) identifying environmental determinants of rhinovirus illness severity (PI, Gern), (v) developing rapid systems for isolating circulating tumor cells (PI, Lang), (vi) understanding transcriptional regulation of GATA switches (PI, Bresnick) and (vii) developing immunotherapeutic agents for melanoma (PI, Sondel). In addition, this cytometer will also support the funded research conducted by 12 minor users. The research focus of the major and minor users covers the gamut of major human maladies and integrates basic, translational and clinical research projects. All projects will benefit from the multi-parameter capabilities of the BD FACSymphony and will allow researchers to study rare cell populations and provide fundamental knowledge of disease processes. The BD FACSymphony requested through this proposal will enable analysis of 35 fluorescent markers and 2 scatter parameters. This same instrument can, in the future, be expanded to conduct analysis of up to 50 parameters. Therefore, this BD FACSymphony will help address the advanced flow cytometry needs of our users for several years in the future. The large major and minor user base ensures that the BD FACSymphony will be utilized for at least 75% of the total AUT. Outstanding continued support from the institution will ensure full financial solvency. A dedicated staff with over 32 years of collective experience in flow cytometry will help maintain a well- tuned BD FACSymphony and assist our users in conducting experiments that are rigorous and reproducible.